I’m frequently asked if sugar causes inflammation. The question seems simple enough, but there’s a lot jammed in there.

My short answer is that a high-sugar Western diet looks to be a key factor in creating systemic, needless immune activity in the human body. And that this immune activity (called chronic inflammation) is linked to every chronic disease in the book.

The long answer requires more nuance. For most people, having a soda doesn’t “fire up” the immune system. No, the links between sugar and inflammation are more subtle. The sugar consumption is usually one or two steps removed from the resulting inflammation.

Consider that:

  • High sugar intake leads to high blood sugar, a pro-inflammatory state.
  • A high-sugar diet may preferentially feed inflammatory bacteria in the gut.
  • Eating sugar (fructose in particular) can cause the liver to produce toxic levels of fat.

But before proceeding, it’s important that we’re on the same page with the terms “sugar” and “inflammation.” They’re often thrown around with vague understanding and plenty of vigorous head-bobbing. In this article, we’ll cover sugar, acute vs. chronic inflammation, and 6 mechanisms by which sugar is linked to inflammation. Let's get started.


The Rundown on Sugar

Sugar is a vague term. It can refer to a variety of things, including:

  • Glucose
  • Fructose
  • Galactose
  • Sucrose
  • High fructose corn syrup
  • Your love interest
  • Giving someone a kiss

The term “refined sugar” (or “added sugar”) is more specific. It generally refers to either sucrose (table sugar) or high fructose corn syrup—both of which are blends of the simple sugars glucose and fructose.

It’s added sugar that’s high in the Standard American Diet (SAD). How high? Believe it or not, the average consumption is about 15 to 20 teaspoons per day!

We add sugar to sauces, soups, dressings, cookies, crackers, trail mix, and anything else that comes in a package. And we REALLY cram it into soda, fruit juice, and so-called “sports drinks”.

Sugar-sweetened beverages (SSBs) account for the majority of our sugar consumption. And they may be the majority driver of our diabetes and obesity problem too.

In one study, women who consumed one or more SSB per day had an 83% higher risk of developing type 2 diabetes vs. women who consumed one or less SSB per month.

Yes, I know correlation doesn’t equal causation, but the mechanisms are there too. It makes sense that swilling empty, non-satiating calories leads to obesity, metabolic issues, and everything that comes with them.

The link to inflammation is less straightforward, but it should become more clear in the next three minutes if you stick around. Let’s geek out on inflammation now.

Acute vs. Chronic Inflammation

Many people are confused about inflammation. They label it “bad” and their thought process ends there.

But inflammation isn’t always bad. Without it, you couldn’t heal from an injury or ward off infection.

So let’s sharpen things up by defining two types of inflammation:

  1. Acute inflammation
  2. Chronic inflammation

Acute inflammation is a temporary immune response to a specific disease, trauma, wound, or infection. It’s your army of immune cells mobilizing to handle a problem.

The first soldiers to arrive are called inflammatory cytokines. They rush to the site and serve as signaling beacons for platelets, lymphocytes, neutrophils, and the rest of your immune system.

This response is how your body fights off pathogens and heals wounds. Without it, every scrape would become horribly infected and possibly kill you. And so acute inflammation is often desirable. (Though not always, as in the case of traumatic brain injury).

Chronic inflammation (aka, systemic inflammation) is never desirable. Like acute inflammation, it involves an immune response with cytokines and white blood cells. But unlike acute inflammation, there is no specific infection that needs to be neutralized.

To have chronic inflammation is to have a chronically-confused immune system. It’s fired up, but it doesn’t have to be. And this has bad consequences.

Most modern diseases—heart disease, cancer, Alzheimer’s, diabetes, you name it—have systemic inflammation in common. As chronic inflammation goes up, expected lifespan goes down.

This is most obvious with heart disease. Inflammation is what forms plaques in the arterial wall—plaques that eventually break off to cause heart attacks and strokes. Some researchers believe that statins work, not because they lower LDL particles (the initial domino in plaque formation), but because they lower inflammation.

By now you’re probably wondering what causes chronic inflammation. Well, how much time do you have?

Poor sleep, aging, cigarette smoking, alcoholism, lack of exercise, and a high intake of vegetable oils are just a few factors that top the list. I believe excess sugar consumption belongs on that list too.

6 Ways Sugar Can Cause Inflammation

When you look at observational data, you find that higher sugar intakes are correlated with higher levels of inflammation. For instance:

  • In 244 healthy women, a high glycemic diet was associated with higher levels of C-reactive protein (CRP)—a marker of non-specific inflammation.
  • Young children who drink more sugary beverages have more inflammation.
  • American consumption of SSBs declined from 1999 to 2010, and CRP declined along with it.

These correlations aren’t enough to convict sugar on the charge of inflammation. But when you combine them with mechanistic data, the case grows stronger.

With that in mind, here are six ways sugar can drive inflammation.

#1: By raising blood sugar levels

High blood sugar (or hyperglycemia) is a proinflammatory state. Why? Because glucose is a highly reactive molecule.

Specifically, glucose reacts with oxygen, creating volatile compounds called reactive oxygen species. This oxidative stress, in turn, creates damage that provokes an inflammatory response.

Where does sugar come in? When someone consumes loads of sugar, that sugar ends up in their blood.

And if they chronically consume loads of sugar, their blood sugar stays chronically high. This is how type 2 diabetes develops, and inflammation is always looming over this disease like a grim specter.

#2: By disrupting gut health

Your gut is home to a vast colony of microbes called the gut microbiome. These microbes influence digestion, mood, and—relevant here—the immune response.

The research is preliminary (mostly in mice and test tubes), but scientists believe that certain classes of bacteria influence inflammation. For instance, excessive levels of Proteobacteria appear to trigger an inflammatory response in animals, while Bacteroidetes seem to have the opposite effect.

And in humans, a diet high in simple sugars was found to increase intestinal permeability.

This increase in intestinal permeability, called leaky gut, means that too many particles slip through the intestines and into the bloodstream. The confused immune system then attacks these particles, creating damage and even more inflammation. Sugar feeds bad bacteria that perpetuate this cycle.

#3: By impairing oral health

Putting sugar in your mouth feeds a pathogenic oral bacteria called Streptococcus mutans (S. mutans). S. mutans then accelerates plaque formation, degrades teeth, and causes cavities.

But S. mutans isn’t just a cavity bug. It often gets into the bloodstream, triggers inflammation, and may increase the risk of heart disease. Another reason to avoid sugar.

#4: By increasing fat production in the liver

Humans have a special taste for fructose. This simple sugar (found in fruit, sucrose, and high fructose corn syrup) served us well in prehistoric times. It’s quick to be stored as fat, so it was useful to fatten us up during times of caloric scarcity. When we ran out of food, we could rely on these fat stores for energy.

In fact, we have a special mutation that shunts fructose to the liver for rapid conversion to fat. Back in the day, the apes that had this mutation were more likely to survive famines, and so it spread through the population naturally.

Humans carry this mutation to this day—and it’s not serving our species well.

This excessive fructose-fat conversion—which occurs whenever we slurp down a soda—has inflammatory consequences. It turns out that making all those fatty acids creates metabolites that probably increase oxidative stress and inflammation.

#5: By decreasing ketone production

When you consume sugar, your blood sugar and insulin levels rise. Rising insulin then shuts down fat burning and ketone production.

Where’s the link to inflammation? Ketones are anti-inflammatory.

Specifically, the ketone body beta-hydroxybutyrate has been shown to suppress the NLRP3 inflammasome—a signaling beacon of chronic inflammation.

#6: By promoting weight gain

The link between obesity and inflammation is complex. They tend to come together, but it’s not clear which is causative.

What’s more clear is that high intakes of added sugar underlie both problems. Why?

For starters, sugar is easy to overconsume. Our genes love sugar—remember that fructose used to confer a survival advantage—so our taste buds lap it up. Plus added sugar is less satiating than fat, protein, or starch… you know, the molecules you find in whole foods.

Then there’s the whole sugar-induced metabolic dysregulation I covered earlier. If you want to stay slim and non-inflamed, added sugar won’t help with those goals.

So whether obesity causes inflammation or inflammation causes obesity, the takeaway is the same: Sugar is not your friend.

Less Sugar, Less Inflammation

If you want to live a long and healthy life, it pays to eat an anti-inflammatory diet. A big part of that means minimizing added sugar.

But that’s just one part of living an anti-inflammatory lifestyle. Sleeping well, exercising regularly, avoiding vegetable oils, managing your stress, and getting all the vitamins and minerals you need.

Today was all about sugar, but health is a holistic endeavor. Since you made it to the end of this article, I have a feeling you already knew that. Keep it up.